1. Field of the Invention
The present invention relates to a non-electromagnetic wave temperature controller for a heating cable and a method therefor, which can perform heating and temperature detection in a non-electromagnetic fashion without short-circuiting one end of the heating cable that is used in warmers, such as electric floors, electric mats and electric fomentation devices. Furthermore, the present invention relates to a temperature detection non-electromagnetic heating cable and a temperature controller, which can reduce the amount of heat and control temperature without using a separate temperature sensor when the temperature of the heating cable is controlled or an arbitrary portion of the heating cable is overheated, and can prevent a magnetic field from being generated in the heating cable without short-circuiting one end of electrical heating wires and intercept the generation of a leakage electric field.
2. Description of the Related Art
Conditions surrounding a bed, such as temperature and humidity, are important factors governing humans' sleep. In order to keep the temperature of a bed appropriate, many homes widely use electrically heated bedding and warmers, such as electric floors, electric mats or electric fomentation devices. Such electrically heated bedding and warmers contain heating cables, so that heat is generated when power is supplied to the heating cables. Accordingly, a temperature controller that detects temperature around a heating cable and controls power supply based on the detected temperature is essential.
In a conventional bedding heating cable, temperature is detected in such a way as to short-circuit one of two parallelly arranged metallic electrical heating wires and provide a temperature sensor separate from a heating cable. However, the method in which the temperature sensor and the heating wire are separated from each other is problematic in that it cannot detect the temperature of the overall heating cable caused by an internal short circuit of the heating cable or local overheating at an arbitrary location. Accordingly, there are problems in that a fire and an electric shock may occur when the heating cable is locally overheated, short-circuited or cut.
Another conventional method includes a method of short-circuiting one end of two parallelly arranged metallic electrical heating wires, installing a separate sensor on the circumferential surface or internal central surface of the end and detecting temperature using a third electric wire. However, the method of detecting temperature using a third electric wire without separating a heating cable wire therefrom is problematic in that a temperature sensor layer and a third metallic layer are added to the heating cable and, therefore, the thickness of a non-magnetic field electrical heating wire increases so that it cannot be used for thin bedding, a manufacturing process of a heating cable is complicated, and manufacturing costs increase. Furthermore, all of the above-described methods have problems in that they have the problem of temperature control of the heating cable, they cannot be used in practice due to the excessive thickness of the heating cable and they cannot intercept harmful electromagnetic waves caused by voltage or current.
Meanwhile, in connection with heating cables, conventional non-magnetic field heating wires used as heating elements for electrically heated bedding and warmers, such as electric floors, electric mats or fomentation mats, each include a core thread formed of a polyester thread or glass wool, a heater coil spirally wound around the core thread, an internal insulation element applied to the heater coil wound around the circumferential surface of the core thread to insulate the heater coil, a shield arranged on the circumferential surface of an internal insulation element in conductor or net form and grounded, and an external insulation element applied to the shield. In the above-described construction, the heater coil and the shield are connected at the ends thereof and electrically in series to each other, and the front ends thereof become power input terminals that are connected to the (+) and (−) terminals of the power source.
The conventional non-magnetic field heating cable has disadvantages in that it is provided with an internal insulation element, so that the thickness of the heating cable is excessive and the flexibility thereof is poor. That is, in the conventional non-magnetic field heating cable for bedding, the internal insulation element is softened by high temperature heat generated from the heater coil during heating and the insulation property of the internal insulation element rapidly degrades, so that the thickness of the internal insulation element should be large so as to prevent the short circuit of the heater coil and the shield. Accordingly, the thickness of the conventional heating cable is at least 6 mm, so that problems arise in that the conventional heating cable protrudes and presses a human's body when the heating cable is applied to an electric mat, and it is almost impossible to apply the conventional heating cable to thin bedding, such as electric mats, electric blankets and electric floors, due to the thickness and flexibility of the conventional heating cable.
In order to solve the above-described problems, the present applicant invented a heating cable. The improved heating cable is advantageous in that the thickness of an internal insulation element is reduced using a heating wire coated with enamel, and performance is not degraded when bending stress is repeatedly applied to the heating cable, since a lead wire is wound around the outer surface of an internal insulation element. By this, the problems of having excessive thickness and poor flexibility can be completely overcome.
However, the improved heating cable cannot perform functions of detecting local overheating and accordingly controlling conduction. When local overheating occurs or the actual temperature exceeds a reference temperature at an arbitrary location of a heating cable of several tens of meters, power is shut off because there is the danger of a fire or a burn. For this purpose, a separate temperature detection device is required. That is, inconvenience arises in that a plurality of temperature detection devices are additionally provided at arbitrary locations to detect the temperature of a long heating cable. These temperature detection devices are configured to protrude outside bedding, thus inconveniencing users. In particular, a problem arises in that it is difficult to attach the temperature detection devices to thin bedding.